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6566-20-720-2101 — WASHER,LOCK

✓ Government record, cited
— · NUT WASHER
PRODUCT OVERVIEW

6566-20-720-2101: WASHER,LOCK.

The WASHER,LOCK is a the manufacturer industrial component. Key specifications include material: STEEL COMP 4340 OVERALL, hardness_rating: 34.0 ROCKWELL C MINIMUM AND 38.0 ROCKWELL C MAXIMUM, surface_treatment: OXIDE OVERALL. This part is cataloged in the U.S.

Government catalog under NSN 5310-01-129-3381, indicating validated use in U.S. government and defense logistics supply chains. Available through authorized enterprise resellers and TPM (Third Party Maintenance) channels.

Verify compatibility with your specific system configuration before ordering.

WHERE IT FITS
6566-20-720-2101
NSN: 5310-01-129-3381
FSC: 5310 — Nuts and Washers
CAGE: 78286 — SIKORSKY AIRCRAFT CORPORATION DBA SIKORSKY AIRCRAFT CORP (USA)
SPECIFICATIONS
materialSTEEL COMP 4340 OVERALL
hardness_rating34.0 ROCKWELL C MINIMUM AND 38.0 ROCKWELL C MAXIMUM
surface_treatmentOXIDE OVERALL
NSN5310-01-129-3381
COMPONENT DIAGRAM
NUT & WASHER — GRADE MATCHING REQUIRED Hex NUT CROSS-SECTION WASHER OD: — SIZE: — MATERIAL: — PN: 6566-20-720-2101 · OEM ⚠ VERIFY BEFORE ORDERING Grade matters for torque spec — don't mix grades. A Grade 5 nut on a Grade 8 bolt weakens the joint. Lock nuts, wing nuts, and castle nuts are NOT interchangeable with standard hex ✓ BROKER TIP Match nut to bolt thread class and material. Stainless bolt + zinc nut = galvanic corrosion. Always verify finish matches (plain, zinc, hot-dip galvanized) PARTSTABLE TECHNICAL DRAWING — NOT TO SCALE
KEY FEATURES
•
HARDNESS RATING: 34.0 ROCKWELL C MINIMUM AND 38.0 ROCKWELL C MAXIMUM
•
COLOR: BLACK OVERALL
•
SURFACE TREATMENT: OXIDE OVERALL
•
MATERIAL: STEEL COMP 4340 OVERALL
TECHNICAL CHARACTERISTICS
HARDNESS RATING34.0 ROCKWELL C MINIMUM AND 38.0 ROCKWELL C MAXIMUM
COLORBLACK OVERALL
SURFACE TREATMENTOXIDE OVERALL
MATERIALSTEEL COMP 4340 OVERALL
OTHER ITEMS IN FSC 5310 — Nuts and Washers
Items in the same Federal Supply class. No interchangeability or substitution relationship is implied.
5310-00-000-0040 5310-00-000-0077 5310-00-000-0079 5310-00-000-1146 5310-00-000-3815 5310-00-000-4532 5310-00-000-4540
SUBSTITUTES & CROSS-REFERENCES

No substitute or cross-reference records for this part.

LIFECYCLE
NSN statusActive· U.S. Government catalog
Acquisition advice: Insurance item — stocked against contingency demandNo demilitarization required
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FREQUENTLY ASKED QUESTIONS
What is 6566-20-720-2101?
6566-20-720-2101 is a WASHER,LOCK.
What is the NSN for 6566-20-720-2101?
6566-20-720-2101 is cataloged in the U.S. Government catalog under NSN 5310-01-129-3381. This indicates validated use in U.S. government and defense supply chains.
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✓ PartsTable — the parts reference. Every fact cited to its source.
PartsTable Design LLC · partstable.com
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-18.
PartsTable commercial catalog: edition Unified commercial catalog snapshot through 2026-09-28, edition date not on file, retrieved 2026-09-28.